标签：[] ++ int style ide instance class space pac
You are given an n x n 2D matrix representing an image.
Rotate the image by 90 degrees (clockwise).
Follow up:
Could you do this in-place?
The idea was firstly transpose the matrix and then flip it symmetrically. For instance,
1 2 3
4 5 6
7 8 9
after transpose, it will be swap(matrix[i][j], matrix[j][i])
1 4 7
2 5 8
3 6 9
Then flip the matrix horizontally. (swap(matrix[i][j], matrix[i][matrix.length-1-j])
7 4 1
8 5 2
9 6 3/** No extra space 2 steps*/ public void rotate(int[][] matrix) { int row = matrix.length; int col = matrix[0].length; for(int i = 0 ; i < row; i++){ for(int j = i; j < col ; j++){ //对角线 int temp = matrix[i][j]; matrix[i][j] = matrix[j][i]; matrix[j][i] = temp; } } // step 1 for(int i = 0 ; i < row; i++){ for(int j = 0; j < row/2 ; j++){ //col -> row int temp = matrix[i][j]; matrix[i][j] = matrix[i][row-1-j]; matrix[i][row-1-j] = temp; } } // step 2 }
标签：[] ++ int style ide instance class space pac
原文地址：http://www.cnblogs.com/joannacode/p/6106098.html
